1. Field of the Invention
The invention relates to a conveyor installation for hanging items, in particular for pieces of clothing hanging on hangers, comprising a transport rail with a bearing; a drive chain which is guided in said bearing and is drivable in a direction of conveyance and which comprises upper coupling members located at a lower side of said drive chain; retaining members for said hanging items, which retaining members are displaceably mounted in the direction of conveyance below the drive chain by means of rollers, with the upper ends of the retaining members being provided with lower coupling members, and with in each case one upper coupling member and one lower coupling member forming a drive connection of the drive chain with a retaining member for conveyance of said retaining member in the direction of conveyance.
2. Background Art
A conveyor installation of this type is known from DE 10 2005 006 455 A1 where a strand of a circulating drive chain, which is drivable in a transport direction, is arranged in a transport rail. The drive chain is embodied with downwardly protruding bolts. Below the drive chain, retaining means are provided which are mounted on rollers in the transport rail, the lower end of which being provided with an opening for receiving the hook of a hanger with a piece of clothing. Each of the retaining means is provided with lugs at their upper ends which project upwards between adjacent bolts so as to form a positive drive connection between the drive chain and the retaining means. The conveyor installation, which is referred to as transport system, comprises no device which allows retaining means to accumulate while the drive chain is being driven continuously.
EP 0 623497 B1 discloses an accumulatable conveyor where a carrier for items to be transported is mounted on a carrier rail via rotatably drivable rollers, the carrier being drivable in a direction of conveyance by a traction means in the form of a friction belt which is also mounted to the transport rail. In order for carriers to accumulate in a desired manner, a stopping device comprising a retaining finger is provided, which retaining finger is extendable into the movement area of the carriers and acts on a spreader device mounted to the carrier, thus causing the carrier to be pivoted laterally and therefore to be lifted off the friction belt.
The disadvantage of this arrangement is that lifting succeeding carriers off the friction belt requires the spreading devices, which are assigned to the individual carriers, to come into direct contact with each other. Lifting the carriers off the friction belt, in other words bringing about a state in which the carrier is not driven, is however impossible if the transported items have a dimension in the direction of conveyance, in other words a thickness, which is greater than the distance of carriers which are in close contact with each other. This results in a frictional drive connection between stopped carriers and the continuously running friction belt, which in turn results in excessive wear and undesirable downtimes required to perform repair works at the conveyor installation. Another disadvantage is that lifting the carrier off the friction belt is performed by pivoting the carrier, which causes the elastically deformable spreading devices of plastic material to be subjected to inertial forces depending on the mass of the trans-ported items, thus resulting in premature wear.
DE 296 21 786 U1 discloses a pawl conveyor where a traction means, which is drivable in a direction of conveyance, is provided with pivotable pawls having a hook-shaped end allowing the pawls to displaceably seize and convey hangers loaded with items to be transported along a rail. The particular shape of the pawls allows hangers to accumulate by means of a device which lifts a pawl by means of a stopping member which comes into contact with the lower side of the pawl and thus disengages the hook-shaped end from the hanger and causes succeeding pawls to be lifted by the hanger which has just been brought to a standstill. One disadvantage of this conveyor is that a continuous accumulation of hangers is only possible if particular design specifications have been determined for the dimensions of the pawls and accordingly, the thickness of the transported items. Another particular disadvantage is that the hook-shaped ends of the pawls may be subjected to an excessive load during an accumulation process if pivoting a pawl is impossible due to a previously transported item having an excessive thickness. The last-mentioned disadvantage is to be remedied by a pawl designed according to DE 299 15 523 U1.
DE 40 17 821 C2 discloses a conveyor installation where carriages for items to be transported are moved along guide rails by means of bristles which are arranged, in the form of drivers, on a driven belt strand and come into frictional contact with a portion of the carriages. If it is desired to accumulate transported items, the carriages are stopped while the bristles keep on moving so that a residual frictional force is exerted on the carriages. In this conveyor installation, the bristles are to act as a slip coupling which forms a releasable drive connection independently of other criteria and allows continuous accumulation of transported items independently of their thickness. In this type of drive connection where the drivers come into engagement with the bristles and are moved relative to each other during an accumulation process, the bristles are subjected to a considerable amount of wear. This results in downtimes required to replace worn-out bristles by new ones.
An overhead conveyor installation is disclosed in DE 297 09 547 U1 where hanger carriers, which are mounted on rollers and are driven by a conveyor chain located thereabove, are movable along a main conveyance path. To this end, the conveyor chain is provided with drivers which are mounted thereto at regular distances and cooperate with rigid coupling members at the hanger carriers. A switch station allows the hanger carriers to be moved to the side, i.e. from the main conveyance path to an accumulation path, which causes the drive connection to be released. The diverted hanger carriers are then driven by a separate drive device. In the region of an accumulation path, a stopping device referred to as accumulation stop is provided where hanger carriers accumulate. As it is required to install a separate, complex drive device for driving the hanger carriers to be accumulated along the accumulation path, the design of the overhead conveyor installation is extremely complicated.